Just wanted to update my experience with the Schumacher SEM-1562A-CA. I've seen it for $17 from Amazon and online only from Wal-Mart. I saw the XM1-5 for sale at a Wal-Mart store though for just under $20. Again, I think they're probably the same under the hood, but where the case and the light positions are different. My box is really light and probably doesn't have a heavy transformer to operate a linear power supply with heavy coils like the old one. It's probably a switched-mode power supply inside, and there's no vent holes. They have a variety of different 1.5A and 3A maintainers, and I'd think they probably use the same guts to some degree. Maybe the 3A version uses a bigger power supply. There's a 1.5A onboard version that only has two lights, but it could be easy to control that function by hardwiring.
So the thing turns on, all three lights cycle, and the yellow light stays on if it's connected to a battery, or all the lights turn off and stay off if they're not. I don't believe this particular unit will detect that it's fully charged for at least several minutes. The older version (I've got an SEM-1562A) had a 6V/12V switch and would shut off almost immediately if you had a near full battery.
This one seems to back off from charging again once it senses that the battery is fully charged. It goes into a "maintain" mode where the green "charged" light pulses like a heartbeat. I removed the clamps from the battery, and it was still pulsing. It didn't stop pulsing until I unplugged it from the outlet. I'm not sure what was going on, but what I did wasn't their recommended procedure, which was to unplug it first before removing the clamps.
This probably isn't strictly a "maintainer" like one of those cheap units from Harbor Freight. HF says only to use those with a fully-charged battery showing at least 12V. The Schumacher maintainers are capable low-current chargers that can slow charge a depleted battery over a few days. If my wife forgets the lights and the battery is depleted, I prefer to hook up this thing overnight rather than jump start it, since a depleted battery is supposed to be tough on the alternator. I'll jump it if there's no other choice, but also use this thing to try and get the battery up to a full charge and hopefully condition the battery. I don't have a faster charger though, but I'm thinking of getting one.
